The form is noun + comparative adjective + than + noun.
The red dress is prettier than the black dress.
Then has a few meanings.
a. in that case –
-- Isabelle – “I am so tired”
-- Sally – “Then maybe you shouldn’t stay up so late”
b. after that –
First I went to Montreal. Then I met Georges St. Pierre. (This indicates a sequence of events.)
c. at that time –
One time I cried while sitting in the dentist’s chair. I haven’t been back since then.
Do you know the difference? Try this quiz.